Sony A77 OLED Viewfinder

Hidden beauty. The new OLED-based "TruFinder" on the Sony A77 is key to its operation, addressing many limitations of past electronic viewfinders.

Long time readers know that we at IR always been lukewarm toward electronic viewfinders (EVFs). Happily, though, EVF technology continues to improve steadily, and the OLED (organic light-emitting diode) viewfinders on the A77, A65, and forthcoming NEX-7 represent another solid advance in the field. Optical viewfinders still can't be beat for clarity and brightness in some environments, but the OLED technology in Sony's latest viewfinders narrows that gap, and there are undeniably many ways in which Sony's new EVFs offer dramatically greater capabilities.

As we've looked back and edited this section, it struck us that there's an awful lot of discussion here about what is, after all, "just" a viewfinder. In defense of this, we think the EVF on Sony's translucent-mirror technology (TMT) and mirrorless NEX models will be a critical factor for a lot of traditionalists in deciding whether to make the move away from their old-style SLRs. Their electronic viewfinders are much more a key component of TMT cameras' value propositions than optical finders ever were in conventional models.

Tonal Range

One of our biggest gripes with EVFs has always been their limited tonal reproduction, particularly in highlight areas: It's enormously frustrating trying to frame a landscape shot with no idea of where the clouds are in the sky. Overall high-key subjects were always a challenge as well.

Sony's new OLED technology does a dramatically better job with highlights than most any EVF approach we've seen in the past, but we found that the tonal problem has now moved to the shadows: In scenes with a wide tonal range, it can be tough to see any detail in shadow areas without momentarily re-framing to get the viewfinder to gain-up a little.

We're optimistic, though, that this issue with tonal range might be addressed in firmware, perhaps even by the time the A77, A65 and certainly the NEX-7 reach market. A big feature OLED has going for it is an incredibly wide dynamic range. At the high end, you're of course limited with how brightly the little LED pixels can shine (more on that in a moment), but at the low end, when an LED is off, it's off: Zero current in means zero light out. By contrast (no pun intended), LCDs work by filtering light coming from a constant-brightness backlight, and so never get really black. So with an OLED, you have much more dynamic range to work with in the first place.

It seems to us that the problem with plugged shadows could be addressed fairly simply by just applying the right tone curve to image data being sent to the OLED unit. On the image-capture side, Sony has a very effective DRO (dynamic range optimizer) option that does a good job of balancing brightness between highlights and shadows. It even works when recording live video. Why not apply the same technology to these new OLED viewfinders, to boost shadow area brightness a little so you can see details?

We say we're optimistic that a firmware patch could better manage the OLED's tonal range, but it's possible that the camera hardware just isn't wired to provide for massaging the data flowing to the OLED chip. Let's all cross our fingers, and see what happens...

Brightness

Before turning to all the positive aspects of EVFs, I'll raise one other area where they lag behind optical viewfinders, namely image brightness compared to bright daylight. While I really fell in love with the Sony A77's EVF, it shared one remaining foible with lesser EVFs of the past. Even with the brightness adjustment set to maximum, when I brought the viewfinder to my eye while shooting under bright sunlight, the EVF display was significantly less bright than the surroundings. I often found it taking a moment for my eyes to adjust to the dimmer view, and I was conscious of pressing the camera particularly closely against my face in an attempt to block out as much ambient light as possible.

I don't know what the brightness limits of OLEDs are, so it's possible that Sony could change the settings to let the EVF get even brighter, but my guess is they'd already have done so if it were feasible. I personally didn't feel that the limited brightness was a major issue, but other IR team members who used the camera in bright sunlight found it rather distracting. (Happily, the transflective rear-panel LCD does well in bright surroundings; it worked very well, even in glaring direct sunlight.)

Sensitivity

Having spent more than my share of time griping, it's time now to turn to the positive aspects of EVFs, as evinced by Sony's OLED technology. One very useful improvement over optical viewfinders comes at the opposite end of the light scale, when shooting under dark conditions. The Sony A77's EVF does an excellent job of gaining-up when the light gets dim. There's no free lunch, in that the trade-offs are that the image gets a bit grainy looking, and the refresh rate drops dramatically, but the net result is I was much more able to see what I was shooting after dark with the A77 than I've ever been with any optical-viewfinder camera I've used in the past.

The first thing you'll notice right off when first looking into the Sony A77's viewfinder is how big it is. Compared to the viewfinders on any other subframe camera, the view through the A77's is enormous. The view has to be a good 30-40% larger in both height and width than what you'll see on most any other subframe camera on the market.

Surprisingly, though, even with its extra-wide viewing angle, the Sony A77 maintains a surprisingly high eyepoint of 27mm from the eyepiece lens and 22mm from the eyepiece frame. As an eyeglass-wearer, I always appreciate a high eyepoint, and with the A77, I didn't feel that I had to mash the camera against my glasses to be able to see the full display. (I did find myself wishing that the A77's viewfinder projected a little further beyond the back of the camera, though: I was quite conscious of how much my nose pressed against the back of the camera. If I left the LCD screen facing outward, huge nose-prints were an ongoing fact of life.)

The second thing you may notice about the Sony A77's viewfinder is its incredibly high resolution. With XGA resolution (1024x768) and 2,359,296 dots, this is easily the highest-resolution EVF we've ever seen. I found I could make out pixels in the text and icons of the information displays if I squinted hard enough, but never had any sense of pixelation in the viewfinder image itself.

The third important visual characteristic of the Sony A77's viewfinder is its 100% frame accuracy. This is absolutely a what-you-see-is-what-you- get viewfinder; it shows you exactly what the sensor is seeing. This is a feature you just don't see in SLRs below professional-grade models, selling for a couple thousand dollars a pop. Making an optical viewfinder with 100% accuracy requires incredibly exacting tolerances, the kind of tolerances that really drive up manufacturing costs. With an electronic viewfinder, it's a relatively simple matter to show the full image that the sensor is seeing. You can get pretty close (98% based on our measurements) with high-end prosumer or low-level pro models like the Canon 7D or Nikon D7000, but they're still not 100% unless you switch to live view mode and accept the AF speed trade-offs that implies. While it's rarely a critical issue in the sort of shots I take personally, I find it annoying that the "through the lens" viewfinder doesn't show me exactly what the camera is going to capture. - So I'm a huge fan of 100% viewfinders, as long as it doesn't cost me another $1,000 in cost of the camera to get one.

Sony A77 Viewfinder Responsiveness: Update Lag and Refresh Rate

Sony's A55 and A33 translucent-mirror SLRs were true breakthrough devices when it came to high-speed continuous shooting at affordable prices, and the Sony A77 and A65 take that capability up another notch, with maximum frame rates of 12 and 10 frames/second respectively.

Despite their very high frame rates, though, we found it difficult to track and frame fast-breaking action with the A33/55, because the image displayed in the viewfinder was always that of the last frame captured, not what was currently happening in front of the lens. Looking through the viewfinder, we were thus always reacting to where the subject was 1/7 second (A33) or 1/10 second (A55) in the past. A tenth of a second may not sound like much, but with a fast-moving subject (and shooters like us unskilled at sports and action photography), it was enough to cause major problems with framing and tracking.

As I'm writing this, we don't have an A55 on hand to compare against the A77, but it appears to us that in high-speed mode, the A77 is still showing the last image captured, rather than the current "live" view. That said, we haven't been as aware of the update-lag problem as much with the A77; we felt more able to track fast-moving subjects with it than was the case with the A33/55. We'd have to spend more time with it in a sports-shooting environment to say for sure how much improved the A77 is over the A55 in this regard, but even if it's still displaying the just-shot images, decreasing the lag from 1/10 to 1/12 second would be a help.

When not in continuous shooting mode, viewfinder responsiveness is a function of refresh rate; essentially the frame rate of the "live movie" that constitutes the viewfinder image. Specs for this are almost never published, in part because the refresh rate is usually a strong function of the amount of light falling on the camera's sensor. In dim lighting, the camera needs longer exposure times for each frame of the movie it's capturing and playing into the viewfinder display, setting an upper limit on the viewfinder's refresh rate. Indeed, as noted above, the Sony A77's refresh rate drops pretty dramatically when faced with very dim shooting conditions. (A trade off we're happy to accept, given that the resulting viewfinder image is much more visible than that from an optical viewfinder under similar circumstances.)

We don't have any way to measure the Sony A77's viewfinder refresh rate under bright lighting conditions, but our sense is that it's quite high: Motion was very smooth and fluid, and we had no sense of a delay or lag between the subject's motion and what we were seeing in the viewfinder.

Low refresh rates were often a bugaboo of early EVFs, but the problem seems pretty completely banished with the combination of the Sony A77's sensor, fast processor, and OLED EVF technology.

Sony A77 Information Display

The area where EVFs completely crush optical viewfinders is of course in on-screen information display. With the whole viewfinder area a full-color high-resolution image display, readout, status and other information can be displayed anywhere you please. Not only that, but full menu displays are a button-press away, so your eye never need leave the viewfinder while operating the camera.

Another often unrecognized advantage of an EVF is that, because the same display is being used for both the viewfinder image and AF point indicators, there's never a problem with ambient light washing out illuminated AF-point displays, or conversely there not being enough light to see ones that are just an LCD overlay. We found the AF point indicators on the A77's EVF particularly well designed. The Sony A77's AF point markers consist of open green squares with thin black outlines around them. The combination of bright and dark elements means active AF points are easy to see regardless of subject brightness: In bright areas, the black outlines make them stand out, while in dark areas, the green lines are easily visible.

Like the A33 and A55 before it, the Sony A77 makes great use of its EVF for information display. A host of basic camera setting and status information is always visible above and below the image area, and thanks to the unusually large viewing angle, the info displays don't cramp the viewfinder image at all. A lot of optional information that can be displayed as well: A shooting display mode provides data for 13 other camera settings overlaid on the viewfinder image, down the left and right sides; a histogram option displays an exposure histogram overlay in the lower right; a graphic display mode overlays virtual shutter speed and aperture indicators, also in the lower right; and a digital level gauge option overlays a red/green two-axis tilt meter in the center of the frame.

The basics. The default information display arranges exposure and status information along the top and bottom edges of the screen, outside the active image area. (Click image for large version.)

Graphic exposure display. Traditionalists can select an analog-style display for shutter speed and aperture. (Click image for large version.)

Histogram. The histogram option floats a live histogram display in the lower right corner. (Click image for large version.)

Electronic level. It's not terribly visible with this subject, but the electronic level function on the A77 works very well. Here, it's indicating that the camera is tilted down (red bars above center), and that it's level left to right (green bars on either side). (Click image for large version.)

ALL the info. The shooting data display mode overlays status information for no less than 13 different camera settings along the sides of the display. These settings can all be accessed directly via the Fn button on the back of the camera. (Click image for large version.)

Menus too. All of the A77's menus are available directly in the viewfinder, and are unusually crisp and clear, thanks to the OLED's very high resolution. (Click image for large version.)

My response to the rich information environment of a well-constructed high-resolution EVF like the Sony A77's reminds me a little of my initial transition to all-digital photography 8 or 9 years ago now. Back then, I didn't realize how much I'd come to appreciate and even depend on the immediate feedback digital offered until I tried taking a trip with only my trusty film SLR in hand. With all my images locked up in film cans, I felt crippled and resolved "never again:" The next trip and ever after, it's been digital all the way.

I'm finding my experience with Sony's rich EVF environment somewhat similar. My everyday SLR (now an incredible 5 years old; definitely time for an upgrade) is a conventional optical-finder model. After using the Sony A77 for a few days, it feels crippling and archaic to go back to the sparse information provided by an old-style optical viewfinder.

Image Preview

Another feature that's of course not even possible with an optical viewfinder is true image preview. Not only are optical viewfinders generally limited in their framing accuracy, they have no way to show what sort of image the camera is about to record: You have no idea in advance of the shot whether the white balance is suitable, how the exposure is looking, etc. And while an optical viewfinder can give you a pretty good depth of field preview, if you're stopping down the lens much at all, the view will likely be too dark to make out the subject, let along judge relative focus.

The Sony A77 Viewfinder: Bottom Line

Much though I'm sure Sony would like me to agree with them that the A77's EVF finally matches all the desirable characteristics of an optical viewfinder, I'm afraid that time hasn't yet arrived: While great progress has been made, even the A77's OLED display doesn't come close to providing the dynamic range of a purely optical system. Likewise, update lag during continuous shooting is still at least somewhat an issue.

That said, though, I can confidently say that all the benefits the Sony A77's EVF brings over optical systems would leave me entirely comfortable switching over to it from my old-school optical-VF SLR without looking back.

Ultimately, the choice of optical vs EVF will come down to personal preferences, so you'll probably want to look through one yourself before making a final decision. For most people, though, I think the benefits of an EVF like the Sony A77's will far outweigh the few remaining limitations.